SCJP 1.6版考題 075

11. public interface A{ public void m1(); }
13. class B implements A{ }
14. class C implements A{ public void m1(){}}
15. class D implements A{ public void m1(int x){}}
16. abstract class E implements A {}
17. abstract class F implements A { public void m1(){} }
18. abstract class G implements A { public void m1(int x){} }
 

What is the result?
  A. Compilation succeeds.
  B. Exactly one class does NOT compile.
  C. Exactly two classes do NOT compile.
  D. Exactly four classes do NOT compile.
  E. Exactly three classes do NOT compile.

解答

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Ans: C

解說:

此題答案是剛好二個類別不會編繹
13行 B類別錯，既然宣告實作介面A，就要提供介面A中的m1()方法
15行 D類別錯，提供的方法不是用來提供m1()方法的實作
說明：類別實作介面會繼承介面的抽象方法1．類別中有抽象的方法，該類別必須為抽象
2．類別若不為抽象，則必須對繼承的抽象方法提供實作